Electromagnetic waves with frequencies in the microwave portion of the electromagnetic spectrum (sometimes referred to as microwaves) have been used to heat, dry or otherwise process materials in a variety of different commercial or industrial applications. When microwaves are applied to a material, the waves cause molecules in the material to vibrate and generate heat. However, microwave energy decreases as the waves penetrate further into the material causing uneven heating of the material. Non-uniform heat distribution results in underexposed and overexposed material in the same batch. Thus, the use of microwave energy is not particularly well-suited for applications that require substantially even heating of the material.